Speed up multi-objective BO tutorial in smoke test mode by reducing number of iterations (#2302)

Summary:
Pull Request resolved: #2302

This reduces the runtime of the slowest cell from 23s to 10s on my machine.

Reviewed By: saitcakmak

Differential Revision: D56262442

fbshipit-source-id: 64e2ce3aacae9f840c60b5751f1670b3c12bb3d4

Author: esantorella

tutorials/multi_objective_bo.ipynb

@@ -431,7 +431,7 @@
         "warnings.filterwarnings(\"ignore\", category=BadInitialCandidatesWarning)\n",
         "warnings.filterwarnings(\"ignore\", category=RuntimeWarning)\n",
         "\n",
-        "N_BATCH = 20 if not SMOKE_TEST else 10\n",
+        "N_BATCH = 20 if not SMOKE_TEST else 5\n",
         "MC_SAMPLES = 128 if not SMOKE_TEST else 16\n",
         "\n",
         "verbose = True\n",